A fill light is a secondary light source used in photography and videography to illuminate and reduce the density of shadows created by the main (key) light. Rather than eliminating shadows entirely, fill light softens them, helping to control the overall contrast of an image and reveal detail in darker areas of the subject.
Fill light can come from a dedicated artificial light source, a reflector bouncing existing light back onto the subject, or even natural ambient light. The balance between the key light and the fill light - known as the lighting ratio - plays a crucial role in determining the mood and style of a photograph. A subtle fill creates a dramatic, high-contrast look, while a stronger fill pr